Speakers from the canton of Lucerne are infamous for spelling Middle High German (MHG) <i> as <e> when communicating in written Swiss German, e.g. Kind (‘child’) as <Chend>. This phenomenon has been examined only impressionistically by phoneticians. This study provides a first account of this peculiarity of Lucerne Swiss German spellers: an analysis of normalised formant frequencies of two underlyingly MHG <i> vowels from 200+ speakers of the Dialäkt Äpp corpus revealed that the Lucerne allophone is in reality [e] for most of the localities examined, which may explain why in vernacular writing, spellers prefer <e> over <i>. Homophony due to this peculiarity can cause misunderstandings in written and oral communication, and possibly has repercussions on the reading and writing development of Lucerne students.